580ex and elan7

[jim_hitchcock]

I have been using the elan7 with a 420ex and have been very happy with the

results. I recently purchased a 580ex and now my exposures are unpredictable,

to say the least, mostly underexposing. My main problem is shooting in Full

Auto. To explain, I photograph crime scenes and can't fool around with

settings for every picture (except certain evidence and conditions). The

majority of photos are of rooms in a house, vehicle interiors, etc., where I

just need a good, clear and undistorted picture.

With the 580ex the subject is exposed properly, however the background and

periphrial is dark. The "background" is only on average 3-7 feet away. I

never had this problem with the 420ex (or Nikon N90s).

Would it be worth the elan 7n w/ETTL II or am I overlooking something with the

580ex? I have read the "EOS Bible" at photonotes and still can't find

anything.

 

Thanks for any advice.

[jim_larson1]

I think we need to look at this closer.

 

Fundamentally, flash exposure is controlled by the camera body, not the flash unit. Both the 420EX and 580EX should produce identical results -> to the limit of the 420EX's maximum power (which is 1/2 e.g. one stop, less than the 580EX).

 

Have you changed what you are doing with the camera? Any changes to custom functions? Have you recently switched to or from manual focusing (that changes flash metering)? Have you recently moved the AF control from the shutter button to the assist button (that makes the flash think you are manual focussing when you shoot)?

 

If I was to invest money. . I wouldn't buy an ETTL-II film camera. . ETTL-II has its own quirks. I would get a digital, so you can see IMMEDIATLEY if you messed up.

 

Shooting mode, btw, is meaningless to the flash system. Unless you set the flash *itself* to manual (the 420EX lacks this control), the flash will always fire in ETTL mode. You can, however, bias the flash output using "Flash exposure compensation". This can be set on the body *or* on the 580EX units back controls (flash over-rides body setting; it is not additive)

 

When you say the subject is exposed and the background / periphery is dark -> that is actually the way the ETTL system is SUPPOSED to work. The flash system is heavily biased to producing correct exposure *at the focal point*. But this behaviour is unaffected by changing the flash unit. Something else is going on.

 

but. . .the 580EX has a series of controls and custom functions which the 420EX lacks -> have one of these been inadvertently been mis-set? Have you mistakenly dialed in exposure compensation on the flash?

[jim_hitchcock]

I checked the settings and everything is the same on the camera and default settings on the flash. I understand why the background is dark with E-TTL, but it was MUCH less with my 420ex. Should the background be that different at such short distances? In a bedroom (say, 12'x14') if I focus on the bed, for instance, the walls, dresser, etc. would be very dark but the bed properly exposed. It seems to almost spot meter the focused area and ignores everything else. I was beginning to think that the auto-zoom head was not covering the focal length of the lens.

Would changing the flash to TTL mode help? As far as going to digital, that is in my near future, which was one of the justifications to buy the 580ex. I currently use a Fuji FinePix S2, however I'm mandated to only supplement film with digital (for court purposes).

 

Thanks for your help!

[jim_larson1]

"It seems to almost spot meter the focused area and ignores everything else."

 

Yes, that is my experience with ETTL on a 10D. BUT. . .this behavior is irresepective of the flash unit. You should get the same result with 420EX, 580EX, or the pop-up flash.

 

Flash zoom is a different question. Might be the answer. I can't check now. . .but the zoom settings may be different on the two flashes (both will zoom between 24 and 105mm. . but the zoom steps may be different). Although, that should not matter -> unless you are shooting wider than 24mm lenses.

 

Do you use bounce flash on one unit and not the other? Do you have a diffuser on one unit and not the other? Maybe a diffuser will address the issue. (I generally use diffusers)

[mark u]

If your subject is close, then there will be inverse square falloff beyond it. If you want more even illumination you should bounce the flash.

[jim_hitchcock]

Thanks for your responses. The inverse square law makes sense, so maybe that's part of the problem. Even illumination is exactly that I'm striving for. I also was expecting the 580ex to perform like my 420ex, with the addition of the extra power when needed. So you could imagine my disgust when I got back my photos with the differences, especially after spending the money for the 580ex.

I also noticed that the flash range meter starts showing an acceptable range at approx. 7' or so with ISO400 film at 1/60 f4.0. Does this seem right? I could shorten the range to about 3' if I underexpose -2, making it 1/60 f8.0. I would expect an "out of range" reading from being too far rather than under 7', especially with 400 speed film.

 

Thanks again for your responses.

[gene_stadelman]

Jim,

 

I purchasd a 580EX last week and did some testing in my living room. Did a direct shot, 45 degree and 90 degree bounce.

 

I am a new guy on this site, but can provide a side by side comparison of these photos, if you wish.

 

Don't know if you can attach photos or not, but the offer stands if you wish to mail direct.

 

Gene Stadelman

 

estadel1@twcny.rr.com

[jim_hitchcock]

Gene,

 

Thanks for the offer and it's definately easier to explain when you see the photos (worth a thousand words?), but they are film and not digital. Are you using digital or film and what were your results?

[stuart_vu]

I guess Jim problem cause by the 580ex has more power than the 420ex then the more you stop-down the lens, the background is more darker. Try to stay with the same f-stop that you used to use with the 420ex. In my experience try to open the lens with one full f-stop and compare. Good luck. Stuart.

[jim_hitchcock]

Well, through trial and error I may be getting closer to a solution (at least for my needs). I took several shots with the camera on P and the flash on auto E-TTL. I then took the same shots with the flash on just TTL. The TTL photos seemed to give me the more "even" flash I was looking for, just slightly underexposed (settings on +0). I've set the FEC to +1/2, so we'll see how that works out. However, the photos with the E-TTL setting turned out perfect. Still too unpredictable to use exclusively. I'll keep experimenting and post results. Hopefully it will be helpfull to someone else with similar problems.